1. Technical Field
The present invention relates to an object detection apparatus to generate parallax information based on a plurality of captured images and to detect an object in an image capturing area based on the parallax information, and a vehicle-mounted device control system, and a program of object detection stored on a recording medium.
2. Related Art
At present, object detection apparatuses that can detect a target object such as obstacles based on a captured image of an area ahead of a vehicle by an image capturing device are used for automobiles, trains, ships, airplanes or the like. These object detection apparatuses are available, for example, as driver support systems such as adaptive cruise control (ACC) to reduce the burden on drivers of vehicles. The driver support systems provide various functions, including a brake-control-and-alert function that alerts the driver to take corrective action to avoid a collision or reduce the impact of the collision, a driving speed adjustment function to maintain a safe minimum distance between vehicles, and a stray prevention function to prevent the vehicle from straying into another lane. To effectively use these functions, various target objects existing around the vehicle need to be recognized with high precision in an image captured ahead of the vehicle, wherein the various target objects are, for example, other vehicles, pedestrians, road objects (lanes, manhole covers), road-side objects (telegraph poles, guard rails, curbstones, median strips), lanes of the vehicle, and objects, which may need to be recognized to avoid collision.
JP-2012-226689-A discloses an environment recognition apparatus that identifies types of target objects based on luminance information and height position information of the target objects in a detection area such as image capturing area. As to the environment recognition apparatus, an identification number for a specific object is assigned to a target portion having luminance included in a luminance area of the specific object, set in advance, to prepare a specific object map.
Then, the height position of each target portion from the road surface is obtained for each target portion assigned with an identification number. The height position of each target portion can be obtained using parallax information computed from data of two images captured by two image capturing devices. Then, if the height position is within the height position range of the specific object identified by the identification number in a specific object table, the concerned target portion is provisionally determined as the concerned specific object.
After this provisional determination, a certain target portion is used as a base point, and other target portion which is within a given horizontal distance range from the certain target portion and within a given relative distance range from the vehicle are grouped as target portions provisionally determined as the same specific object (i.e., assigned with the same identification number), and the grouped target portions are determined as a target object. Then, a width of the determined target object is computed. If the computed width is within a width range of the concerned specific object in the specific object table, the target object is determined as the concerned specific object.
Three types of information such as height, width (horizontal direction length), distance from the image capturing device to an object in the image capturing area become key information when selectively detecting each of objects in the image capturing area with high precision because one face having the same distance from the image capturing device and having a certain height and a certain width can be assumed as one face of an object, and the above mentioned three types of information is required to identify such one face.
In the environment recognition apparatus disclosed in JP-2012-226689-A, a group of target portions existing in a given height position range and having the same or similar level of luminance is provisionally determined as one target object, and the group of target portions is further grouped of target portions existing within a given horizontal distance range and at within a given relative distance range (distance to the concerned object). Therefore, the environment recognition apparatus disclosed in JP-2012-226689-A may selectively detects each of the target object using three information of object such as height, width, and distance.
However, in the environment recognition apparatus disclosed in JP-2012-226689-A, three types of information of object such as height, width, and distance may need to obtain one by one sequentially. Specifically, at first, target portions having the same or similar luminance and existing in a certain height position range are provisionally determined as one target object, with which height information of the target object is obtained. Then, in a process of identifying target portions existing within a given horizontal distance range, width information of the target object is obtained. Then, in a process of identifying the target portions existing within a given relative distance range, distance information to the target object is obtained. Because three types of information of height, width, and distance of object is obtained one by one sequentially, an object detection processing that selectively detects each object may require a longer time, which is not preferable.